Sheppard Lucy J, Cape J N, Leith I D
Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian EH26 OQB.
New Phytol. 1993 Aug;124(4):595-605. doi: 10.1111/j.1469-8137.1993.tb03849.x.
Two-year-old red spruce (Picea rubens Sarg.) was grown in replicated open-top chambers supplied with charcoal-filtered air near Edinburgh, Scotland. Between May and November 1989, plants were exposed to four mist treatments, three containing sulphuric acid and ammonium nitrate in equimolar concentrations at 0.005 mol m (pH 5) or 1.0 mol m (pH 27), and a fourth treatment with sulphuric acid alone at 1.0 mol m (equivalent to 2 mm precipitation). Two dose rates were used for the pH 2.7 treatment equivalent to 2 and 8 mm of rain per week. Three subtreatments (soil surface exposed to mist, addition of extra sulphuric acid to the soil surface, exclusion of mist from the soil) were included in each chamber. Frost hardiness was assessed by measuring rates of electrolyte leakage after controlled freezing of detached shoots. At the end of October, frost hardiness, expressed as the lethal temperature for 50% of shoots (LT ), was decreased by 8 °C in the 8 mm wk treatment at pH 27, compared to pH 5. The 2 mm wk treatment at pH 2.7 had no effect on frost hardiness either when ammonium nitrate was present or absent (i.e. sulphuric acid only). Excluding mist from the soil, and adding extra sulphuric acid, both increased frost hardiness by about 3 °C when compared with uncovered soil. Excluding mist from the soil increased the amount of foliage initiated and produced inside the chambers but neither subtreatment, excluding the mist nor providing additional sulphuric acid to the soil affected foliar nutrient concentrations. Mist of pH 27 as sulphuric acid alone and in combination with ammonium nitrate both enhanced N uptake. Several observations concerning the effect of acidic mist on frost hardiness were confirmed by this study: (i) preventing mist from reaching the soil/roots, improving conditions for root growth can ameliorate the effects of acidic mist on shoot growth and frost hardiness; (ii) the effect was determined by the ion dose but not by the ion concentration in the mist; (iii) the effect was primarily mediated through foliar absorption; (iv) the presence of high foliar nitrogen concentrations did not increase frost hardiness when foliar sulphur concentrations were also high; (v) low N concentrations were more important for frost hardiness than high foliar N concentrations.
两岁的红云杉（Picea rubens Sarg.）在苏格兰爱丁堡附近配备活性炭过滤空气的重复开顶式气室中种植。1989年5月至11月期间，植株接受了四种喷雾处理，三种处理中硫酸和硝酸铵的浓度为等摩尔浓度，分别为0.005 mol/m（pH 5）或1.0 mol/m（pH 2.7），第四种处理仅为1.0 mol/m的硫酸（相当于2毫米降水量）。pH 2.7的处理使用了两种剂量率，分别相当于每周2毫米和8毫米的降雨量。每个气室包含三个亚处理（土壤表面暴露于喷雾、向土壤表面添加额外硫酸、土壤不接触喷雾）。通过测量离体枝条在控制冷冻后的电解质渗漏率来评估抗冻性。10月底，与pH 5相比，pH 2.7的8毫米/周处理中，以50%枝条的致死温度（LT）表示的抗冻性降低了8℃。pH 2.7的2毫米/周处理，无论是否存在硝酸铵（即仅硫酸），对抗冻性均无影响。与未覆盖土壤相比，土壤不接触喷雾以及添加额外硫酸，均使抗冻性提高了约3℃。土壤不接触喷雾增加了气室内新长出和产生的叶片数量，但排除喷雾和向土壤提供额外硫酸这两种亚处理均未影响叶片养分浓度。单独以硫酸形式以及与硝酸铵结合的pH 2.7喷雾均增强了氮的吸收。本研究证实了关于酸性喷雾对抗冻性影响的几个观察结果：（i）防止喷雾到达土壤/根系，改善根系生长条件可减轻酸性喷雾对枝条生长和抗冻性的影响；（ii）影响由离子剂量而非喷雾中的离子浓度决定；（iii）影响主要通过叶片吸收介导；（iv）当叶片硫浓度也较高时，高叶片氮浓度不会增加抗冻性；（v）低氮浓度对抗冻性比高叶片氮浓度更重要。
